In recent years, technologies of providing three-dimensional images (still images and moving images) which have a stereoscopic effect and a sense of depth to the viewer's eye are becoming popular. However, not everyone possesses the ability to perceive three-dimensional pictures having such properties (binocular vision). Binocular vision in general is broken into simultaneous perception, fusion, and stereoscopic vision. Simultaneous perception is a function of merging and simultaneously viewing different images on the left retina and the right retina. Fusion is a function of fusing substantially the same retinal images at retinal corresponding points on the left eye and the right eye, and perceiving the images as a single object. Stereoscopic vision is a function of perceiving a stereoscopic effect from a disparity between the images due to binocular parallax after fusion is established. A viewer who has a problem with these functions cannot enjoy three-dimensional images. In addition, because visuoperceptual phenomena of this type are personal and subjective, sharing/comparing with others is difficult, which hinders a person with defective binocular vision from recognizing the defect.
In Cited Document 1, there is proposed a stereoscopic vision testing device for determining whether or not a subject's stereoscopic vision is sound based on whether or not the subject is capable of recognizing a three-dimensional-index image. Stereoscopic vision is an ability to perceive an object stereoscopically through the fusion of binocular images, specifically, an ability to sense a slight difference in depth between two points through the fusion of binocular images. Stereoscopic vision is hereinafter referred to as binocular vision.